Mercury bioaccumulation and effects on birds in San Francisco Bay

September 1, 2008

Highlights

San Francisco Bay is an important wintering and breeding ground for more than 1 million waterbirds annually
Mercury concentrations are highest in birds that eat fish and that reside in the Lower South Bay
When Forster’s terns arrive in the Bay in spring to breed, mercury concentrations in their blood increase by four-fold in a six week period
Based on mercury concentrations in blood, nearly 60% of all breeding Forster’s terns sampled in the Bay are at high risk of toxic effects
One important piece of evidence of impairment of reproduction in Forster’s terns is that average mercury concentrations in failed to-hatch eggs were statistically significantly higher than in randomly selected eggs
Avian eggs represent an ideal matrix for assessing bioaccumulation because they are indicative of short-term, localized exposure and are central to predicting risk in multiple lifestages

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